The photophysical properties of a heavy atom-free Bodipy derivative with twisted π-conjugation framework were studied. Efficient intersystem crossing (ISC. Quantum yield: 56%) and exceptionally long-lived triplet state wereobserved (4.5 ms....
The reliable calculation of the phosphorescence energies of phosphor materials is at the core of designing efficient phosphorescent organic light-emitting diodes (PhOLEDs). Therefore, it is of paramount importance to have a robust computational protocol to perform those calculations in a black-box manner. In this work, we use Domain Based Local Pair Natural Orbital Coupled Cluster theory with single, double and perturbative triple excitation (DLPNO-CCSD(T)) calculations to attain the phosphorescence energies of a large pool of Pt (II) complexes. Several approaches to incorporate relativistic effects in our calculations were tested. In addition, we have used the DLPNO-CCSD(T) values (i.e., our best theoretical values) to assess the performance of different flavors of density functional theory including pure, hybrid, meta-hybrid, and range-separated functionals. Among the tested functionals, the M06HF functional provides the best values as compared with the DLPNO-CCSD(T) ones, with a mean absolute deviation (MAD) value of 0.14 eV. In its turn, and thanks to the increased accuracy achieved in the calculation of phosphorescence energies, we also demonstrate that not all the investigated complexes emit from their lowest lying triplet-state (T 1 ). The outlier complexes include different complex photophysical scenarios and both Kasha and anti-Kasha types of complexes. Finally, we provide a general computational protocol to pre-screen whether T 1 is actually the emissive state and to accurately calculate the phosphorescence energies of Pt (II) complexes. 57 Different xc functionals including pure functionals (BP86 58,59 , B97D 60 ), range-separated hybrid
The interplay between noncovalent interactions involving metal complexes may lead to the formation of aggregates (i.e., ground state dimers, trimers, n-mers, etc.), and this is often linked to dramatic changes in their physical and chemical properties as compared to the original properties of the isolated units. Dimers and trimers can also be formed in the excited state potential energy surfaces, i.e., excimers. Excimers are short-lived but are also often characterized by different optical properties from those of the isolated units. Understanding the nature of noncovalent interactions and the presence or not of cooperativity effects in both aggregates and excimers is thus extremely important to rationalize these variations. In this study, we present computational investigations on isoquinolinyl pyrazolate Pt(II) complexes. Our results highlight that cooperativity effects between noncovalent interactions, which are modulated by sterically demanding substituents and metallophilic Pt•••Pt interactions, are present only on certain investigated excimers. We use density functional theory (DFT) calculations to examine the cooperativity effects and the changes in the photophysical properties. Different descriptors of cooperativity effects between noncovalent interactions, including the synergetic, genuine nonadditive, and total interaction energies, were evaluated for a series of Pt(II) aggregates and excimers. In addition, energy decomposition analysis (EDA) calculations were performed to rationalize the origins of the cooperative effects. The cooperative effects in trimer excimers (in their lowest triplet excited state, i.e., T 1 ) led to shortened Pt••• Pt contacts as compared to the trimer aggregates. Furthermore, this synergy between noncovalent interactions is ultimately responsible for the formation of the excimers and the striking changes in the measured photophysical properties. More in detail, we report a change in the character of the lowest-lying triplet excited state when going from dimer excimers (i.e., of mixed triplet ligandcentered and triplet metal-to-ligand charge transfer ( 3 LC/ 3 MLCT) character) to trimer excimers (i.e., of triplet metal−metal-toligand charge transfer ( 3 MMLCT) character). The EDA reveals that the total interaction energy on trimer excimers is subtly controlled by the electrostatic and dispersion terms.
Two indoles linked by a C–C bond have recently emerged as promising scaffolds in medicinal chemistry. Their synthesis, however, involves a multitude of reaction steps. So far, the direct C–H/C–H cross-coupling of two similar heteroaromatics lacking directing groups remains particularly challenging. Transition metals are often added as wasteful sacrificial oxidants to influence the selectivity in Pd-catalyzed C–H/C–H couplings. In this work, we report on the selective C–H/C–H cross-coupling of N-substituted indoles without directing groups, driven by molecular oxygen under mild conditions. The selectivity of the C–H activations was studied via kinetic experiments and computational investigations. A quantitative Hammett study of the aromatic carboxylate ligands shows that regioselectivity can be directed by rationally tuning their electronic properties. This ligand-controlled selectivity can be exploited to obtain selective cross-coupling between two indoles with different substitution patterns, as demonstrated in the synthesis of a potent insulin-like growth factor inhibitor.
Facile access to 4,3-fused 1,2,4-triazolyl-isoquinolines, pyridines and phenanthridines is achieved through electrophilic diazomethylation of the azaarenes with hypervalent iodine diazo reagents followed by 1,5-cyclization of the resulting ammonium diazonium ylides.
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